Acause of disease is an event, condition, or characteristic that preceded the disease and without which the disease would either not have occurred or would have occurred later.

true

The cause of a disease is also called etiology.  The cause must happen before the disease develop. Without the cause, the disease shouldn't appear too.
This makes the research to determine a cause of disease have to take the examination in multiple times. A research that takes one time data like cross-sectional won't show causation.